The source of the song is not generally known amongst Beatle fans. In 1965, a British newspaper, "The Liverpool and London Echo", ran an anti-Fab editorial in which they said that the Beatles could sing the telephone directory, and get a hit out of it, so undiscriminating were the fans.
Immediately the provocative Lennon decided to do just that. The Beatles recorded a 7-minute track singing from late S and early T in the telephone directory, including intitials and addresses and telephone numbers. Then EMI put pressure on that they should remove the phone numbers. John could not see the point, as people, knowing the name, could look up the number.
No sooner was this out of John's mouth that the phrase he had used "You Know My Name (Look Up The Number)" became the catchphrase of this great new song. It evolved quickly into the track we know and love today.
D'ya
believe me?